What is wrong with my neural networks prediction code? All predictions are returning the same class name for every image - tensorflow

Question

Here is my training code:
def train():
#START
img_input = layers.Input(shape=(150, 150, 3))
x = layers.Conv2D(16, 3, activation='relu')(img_input)
x = layers.MaxPooling2D(2)(x)
x = layers.Conv2D(32, 3, activation='relu')(x)
x = layers.MaxPooling2D(2)(x)
x = layers.Conv2D(64, 3, activation='relu')(x)
x = layers.MaxPooling2D(2)(x)
x = layers.Flatten()(x)
x = layers.Dense(512, activation='relu')(x)
output = layers.Dense(1, activation='sigmoid')(x)
model = Model(img_input, output)
model.compile(loss='binary_crossentropy',
optimizer=RMSprop(lr=0.001),
metrics=['acc'])
#END
# All images will be rescaled by 1./255
train_datagen = ImageDataGenerator(rescale=1./255)
val_datagen = ImageDataGenerator(rescale=1./255)
bs = 20
# Flow training images in batches of 20 using train_datagen generator
train_generator = train_datagen.flow_from_directory(
train_dir, # This is the source directory for training images
target_size=(150, 150), # All images will be resized to 150x150
batch_size=bs,
# Since we use binary_crossentropy loss, we need binary labels
class_mode='binary')
# Flow validation images in batches of 20 using val_datagen generator
validation_generator = val_datagen.flow_from_directory(
validation_dir,
target_size=(150, 150),
batch_size=bs,
class_mode='binary')
history = model.fit(
train_generator,
steps_per_epoch=train_steps,
epochs=4,
validation_data=validation_generator,
validation_steps=val_steps,
verbose=1)
model.save_weights("trained_weights.h5")
Here is my prediction code:
def evaluate(imgpath):
if not os.path.isfile(imgpath):
print("No such file: {}".format(imgpath))
sys.exit(-1)
# START
img_input = layers.Input(shape=(150, 150, 3))
x = layers.Conv2D(16, 3, activation='relu')(img_input)
x = layers.MaxPooling2D(2)(x)
x = layers.Conv2D(32, 3, activation='relu')(x)
x = layers.MaxPooling2D(2)(x)
x = layers.Conv2D(64, 3, activation='relu')(x)
x = layers.MaxPooling2D(2)(x)
x = layers.Flatten()(x)
x = layers.Dense(512, activation='relu')(x)
output = layers.Dense(1, activation='sigmoid')(x)
model = Model(img_input, output)
model.compile(loss='binary_crossentropy',
optimizer=RMSprop(lr=0.001),
metrics=['acc'])
# END
model.load_weights("trained_weights.h5")
img = image.load_img(path=imgpath,grayscale=False,target_size=(150,150),color_mode='rgb')
img_arr = image.img_to_array(img)
test_img = np.expand_dims(img_arr, axis=0)
y_prob = model.predict(test_img)
classname = y_prob.argmax(axis=-1)
print("Class: ",classname)
return classname
I have a feeling that the error is somewhere in the last 5-6 lines of the evaluate function, where I am loading the image. The problem is that whenever I run the evaluate function for any image, my output is [0]. Even though the training went well, as seen in the image below.
enter image description here
Am I making some silly mistake somewhere?

Answer 1

since you have a single neuron as the top layer, when you do predictions you will get a single prediction. Since you have a single prediction using argmax will always return 0. What you need to do is to set a threshold value for the prediction for example
if yprob>=.5:
klass=1
else:
klass=0
Also as pointed out by Dr. Snoopy you should rescale your image by 1/255.